In full-dimension MIMO systems (massive MIMO systems) there are control and reference signals that are specific to individual users, but there are also control and reference signals that are specific to the complete cell (e.g. so called cell-specific reference signals/CRS). The cell-specific reference signals are usually transmitted on dedicated logical antenna ports, which bypass the user's precoding. The size and shape of a cell is actually defined as the area in which these signals are transmitted. Therefore, the shape of the beams that carry these cell-specific signals (in form of broadcast beams) should be stable and comply with tough requirements to meet specifications. These specifications are derived from the network planning requirements, and assuming that massive MIMO mobile networks will follow today's cellular approach, it should be expected that the main broadcast beam of massive MIMO networks will follow the specifications of today's antenna panels (3 dB horizontal beamwidth (hor. BW.) of 60 degrees, 10 dB hor. BW. of 120 degrees etc.). Therefore, the shaping of the broadcast beams for massive MIMO antennas is an important and system relevant step and is accomplished by exciting the physical antenna ports with the right amplitudes and weights, which satisfy the requirements for the broadcast beam and also maximize the output power of the transmitting amplifiers.
However, in current MIMO systems, phase and amplitude errors occur, for example in phase or amplitude calibration processes of the signals fed to the antenna element array.